Carbon nanotubes have several desirable properties, including high thermal conductivity, high mechanical strength and hardness, and excellent conducting or semiconducting properties. Accordingly, carbon nanotubes can be beneficially used in a wide variety of applications. For example, carbon nanotubes can be used in the manufacture of electrical energy storage devices (e.g., as a spring or a battery component), for microelectronic devices (e.g., transistors, non-volatile memory, photonic devices, and the like), for medical devices or systems (e.g., bio sensors, drug delivery systems, and tissue engineering), as protective coatings, and many others to provide desired performance of such devices or systems.
Carbon nanotubes can be formed using several different techniques, including laser ablation, arc discharge, electrolysis, and chemical vapor deposition (CVD). Of these various techniques, CVD is generally thought to be the most suitable for high-volume manufacturing of carbon nanotubes.
CVD carbon nanotube formation techniques generally use a metal nanoparticle catalyst on a surface of a substrate. The diameter of the nanotubes and properties of the nanotubes generally correspond to the type and size of the metal catalyst nanoparticle on the substrate surface. Unfortunately, location and size of the metal catalyst nanoparticles are difficult to control. As a result, the growth location and direction, size, chirality, and properties (e.g., band gap) of carbon nanotubes formed using these techniques are also difficult to control.
One technique that has been proposed for forming aligned carbon nanotubes includes electron beam induced deposition of nanoparticle metal catalyst material onto a substrate surface. It is thought that electron beam induced deposition will be able to control the location and size of the deposited catalyst onto the substrate surface. However, such techniques are relatedly slow and expensive and thus are not well suited for high-volume manufacturing.
Crystalline substrates, such as quartz substrates, have been used to form aligned carbon nanotubes, offering some control of the size and chirality of the carbon nanotubes formed using the quartz substrates. However, carbon nanotubes formed using such techniques generally require transfer to another substrate—e.g., a device suitable substrate that includes various layers used to form a device. As a result, the techniques are also not generally suitable for high-volume manufacturing of devices that include carbon nanotubes.
Accordingly, improved methods of forming aligned carbon nanotubes, including methods suitable for high-volume manufacturing, and structures and devices including carbon nanotubes, are desired.